公开(公告)号：US12174413B2

公开(公告)日：2024-12-24

申请号：US18024559

申请日：2020-09-09

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Ryota Imada ,  Yoko Yamashita ,  Takashi Matsui ,  Taiji Sakamoto ,  Nobutomo Hanzawa ,  Noriyuki Araki ,  Shinichi Aozasa ,  Yuto Sagae ,  Kazuhide Nakajima

IPC: G02B6/02

Abstract: Provided are an LPFG and an optical transmission system in which a mode conversion amount does not depend on a polarization state and an electric field distribution. The LPFG according to the present invention includes cavity rows (25-1 and 25-2) of cavities 15 periodically arranged in a core region 11 of the few-mode fiber 10 at a position away from a central axis z of the core region 11 in parallel with the central axis z. Each of the cavity rows (25-1 and 25-2) is located at a different position in a longitudinal direction of the few-mode fiber 10 (where the position in a z direction is different), and the cavity rows (25-1 and 25-2) are located at positions shifted by 90° on a cross section of the core region 11 with the center of the cross section of the core region 11 (the intersection of an x-axis and a y-axis) as an origin.